Cabbage in Zone 8B — Southern California

Cabbage is a fantastic addition to the SoCal garden, offering a satisfying crunch and mild flavor that's delicious raw in salads or cooked in stir-fries. Its versatility in the kitchen makes it a rewarding crop, especially since you can enjoy a fresh, homegrown harvest during our mild winters and into the spring.

While we face challenges like periodic drought and intense summer heat inland, careful timing allows us to grow cabbage successfully. Our long growing season, often stretching close to 300 days, means you can harvest cabbage before the worst of the summer heat arrives.

Starting cabbage indoors gives you a head start, especially with our very-early spring. Begin sowing seeds indoors from mid December through early January, about six weeks before you plan to transplant. Use seed trays filled with a good seed-starting mix.

Keep the trays in a warm location and provide plenty of light, either from a sunny window or a grow light. Bottom watering is an excellent technique to keep the soil consistently moist without disturbing the delicate seedlings.

Transplant your cabbage seedlings outdoors from early February through early March, once they have developed several true leaves. Before transplanting, harden off the seedlings by gradually exposing them to outdoor conditions for about a week. This helps them adjust to the sun and wind.

Space the plants 12-18 inches apart in a sunny spot with well-drained soil. Keep an eye on the weather forecast for any late cold snaps, which are always a risk at this time of year, especially inland.

Cabbage needs consistent moisture to thrive, but overwatering can be just as detrimental, especially with our clay soils in some areas. Aim to keep the soil evenly moist, but not soggy. The "finger test" is your best friend: stick your finger about two inches deep into the soil; if it feels dry, it's time to water.

During our winter-wet season, you might not need to water at all, letting rainfall do the work. As the weather warms up in late spring, increase watering to about 1-2 inches per week, depending on rainfall and soil drainage. Water at the base of the plants to avoid wetting the foliage, which can encourage fungal diseases, especially if you live closer to the coast with its slightly higher humidity.

Signs of underwatering include wilting leaves and slow growth. Overwatering can lead to yellowing leaves and root rot. Mulching around your cabbage plants with straw or wood chips helps retain moisture and regulate soil temperature, which is especially helpful as we head into warmer weather.

You can expect your first cabbage harvest from mid April through late May, about 70 days after transplanting. The best way to determine if a cabbage head is ready to harvest is to gently squeeze it. It should feel firm and solid.

Also, check that it has reached the full size expected for its variety. To harvest, use a sharp knife to cut the head off at the base of the plant, leaving the lower leaves and root system intact.

As our first frost approaches in early December, harvest any remaining cabbage heads, even if they aren't quite fully mature, to avoid frost damage. You can use these smaller heads in soups or stews.

Cabbage Worms

• What it looks like: Smooth green caterpillars chewing irregular holes in leaves, leaving dark green droppings behind. You might also see white cabbage butterflies fluttering around.
• What causes it: Larvae of white cabbage butterflies, which can have multiple generations in our long, warm growing season.
• How to fix/prevent it: Bt spray is very effective and safe for organic gardening. Floating row covers will prevent the butterflies from laying eggs. Handpicking caterpillars is also an option. Interplant with aromatic herbs like thyme and sage to deter the butterflies, and encourage parasitic wasps to help control the population.

Cabbage Loopers

• What it looks like: Similar to cabbage worms, but these are light green with a distinctive looping motion when they move. They also chew holes in leaves.
• What causes it: These are the larvae of a gray-brown moth. Like cabbage worms, they thrive in our warm climate.
• How to fix/prevent it: Bt spray is also effective against cabbage loopers. Handpicking can work for small infestations. Encourage beneficial insects like lacewings and parasitic wasps.

Splitting

• What it looks like: The cabbage head cracks open.
• What causes it: Inconsistent watering. A sudden heavy watering after a dry spell causes the head to swell too quickly, leading to splitting. This is especially common with our unpredictable winter rainfall.
• How to fix/prevent it: Maintain consistent soil moisture. Water deeply but infrequently. Mulch to help retain moisture. If heavy rain is predicted after a dry spell, consider harvesting any nearly-mature heads to prevent splitting.

Clubroot

• What it looks like: Stunted growth, wilting in the afternoon heat (even with adequate water), and yellowing leaves. When you dig up the plant, the roots are swollen, distorted, and club-shaped.
• What causes it: A soil-borne pathogen (Plasmodiophora brassicae) that can persist in the soil for many years. It favors acidic, wet soil.
• How to fix/prevent it: Raise the soil pH to 7.0-7.2 with lime. Improve soil drainage. Rotate brassicas on a 7-year cycle. Remove and destroy infected plants (don't compost them!). Start transplants in sterile potting mix to avoid introducing the pathogen.

Southern California Specific Challenges: Our hot inland heat can stress cabbage plants, making them more susceptible to pests and diseases. Consistent watering is key, but be mindful of water restrictions. Santa Ana winds can quickly dry out the soil, so monitor moisture levels closely during these events.

Green beans make excellent companions for cabbage because they fix nitrogen in the soil, which benefits the cabbage. Celery also works well, as its strong scent can help deter cabbage moths. Onions and dill are great companions as well, because their pungent odors repel many common cabbage pests.

Avoid planting cabbage near tomatoes, strawberries, or peppers. Tomatoes and peppers can stunt the growth of cabbage, while strawberries compete for resources in the soil.